1. Field of the Invention
The present invention relates to an identification device, an identification method, and a storage medium, and more particularly to a technique of performing personal or individual identification by detecting a human face area from image data.
2. Description of the Related Art
There has generally been known a technique of performing personal identification using a face detection function. In this technique, face area feature data specific to each person is extracted from face image data, and a comparison is performed between feature data registered in advance and the extracted feature data. Then, it is determined, based on the result of the comparison, whether or not the face image data matches a registered person.
By the way, feature data is influenced by the facial expression and/or facing direction of a human face area and a situation including a lighting condition. For this reason, when there is a difference between a situation where feature data was extracted and registered and a situation where feature data is extracted from face image data for personal identification, accuracy in personal identification can be degraded.
In order to avoid the degradation of accuracy in personal identification, a method can be employed in which a facial expression is identified from a human face area and then identification is performed using a person database in which feature data of facial expressions is registered. In this method, if feature data corresponding to the identified facial expression has not been registered yet, the feature data is additionally registered (see Japanese Patent Laid-Open Publication No. 2010-27035).
Further, a method has been disclosed in which a plurality of face images continuously picked up from a person and a plurality of face images of the same person registered in advance in a person database are compared with a reference image selected from the face image, and a plurality of face images are selected based on the results of the comparison to thereby update face images in the person database (see Japanese Patent Laid-Open Publication No. 2007-179224).
However, in the method disclosed in Japanese Patent Laid-Open Publication No. 2010-27035, only when identification of a person has already been successful and a facial expression which has not been registered yet as feature data can be detected from the person, additional registration is performed. Consequently, when a change in facial expression and a facing direction of a face, which cannot be detected, or a change in other conditions, including the lighting condition, occurs, it is impossible to improve accuracy in identification.
On the other hand, according to the method disclosed in Japanese Patent Laid-Open Publication No. 2007-179224, face images selected for update vary with a reference image which is selected. This makes the accuracy in identification unstable. Further, whenever an image of a person (i.e. a human face) is picked up, processing for updating the person database is executed, which increases processing load.